This review focuses on deep sea mining (DSM) technology and covers topics such as deep sea mineral deposits, DSM techniques, environmental and legal aspects, consultants, and publications relevant to these topics.
Deep sea mining is a method to retrieve mineral resources from the ocean floor, such as metaliferous oxides and metaliferous sulfides. Oceanic bed sites are characterized by the presence of polymetallic nodules and hydrothermal vents that are rich in minerals like gold, silver, copper, manganese, cobalt and zinc. The deposits are located at depths of 1,000 m to 4,000 m below the sea floor, and are either pumped to the surface or mined through a bucket/dredging system, using a robotic deep sea mining system.
One of the major questions around deep sea mining is whether this vast resource can be excavated in a large-scale, economically viable way without disturbing the unique ecosystem located near the deep hydrothermal vents where the minerals accumulate? There is a lot of debate surrounding this question, from all stakeholders involved, including governments, NGOs, exploration companies, and local communities. There have been conferences taking place to discuss deep sea mining, including the 3rd Annual Deep Sea Mining Summit held in Scotland, UK, in February 2015, and the Asia-Pacific Deep Sea Mining summit held in Singapore in September 2015. Visit deepsea-mining-summit.com for more information about these meetings.
Wikipedia lists the presence of the following mineral resources at varied sea depths:
|Type of mineral deposit
||4,000 - 6,000 m
||Nickel, copper, cobalt, and manganese
||800 - 2,400 m
||Mainly cobalt, some vanadium, molybdenum and platinum
||1,400 - 3,700 m
||Copper, lead and zinc some gold and silver
Oceanflore have details on deep sea mining markets on a wide variety of mineral deposits, including offshore diamonds, offshore phosphates, iron sands, manganese nodules, and seafloor massive sulfides (SMS). Nautilus Minerals is an underwater mineral exploration company headquartered in Toronto, Canada. It is the first company to commercially explore the seafloor for massive sulphide systems. The company was granted the world's first ever deep sea mining license in 2011. The government of Papua New Guinea granted the license to develop the Solwara 1 deposit which is at a depth of about 1,600 m below the sea surface. According to the company's website, the Solwara 1 deposit contains a copper grade of approximately 7%. In addition, gold grades of well over 20 g/tonne have been recorded in some intercepts, with an average grade of approximately 6 g/tonne.
DEEP SEA MINING (DSM) PROCEDURES
After the potential mineral resources have been identified and assessed, trial mining may begin. The main workhorse of deep sea mining is the remotely operated vehicle (ROV) which mainly comprises of three components - drive body, ore crusher and ore lifter.
Nautilus Minerals proposed the use of two 1,000 hp ROVs fitted with drum cutters originally used in terrestrial coal extraction. More details on exploration, mining using ROVs and cutters, risers (ore-lifters), transportation, processing and siting of these process facilities are mentioned in the report Potential Deep-Sea Mining of Seafloor Massive Sulfides.
The table below identifies the organizations involved in nodule mining experiments, mentioning the time span and depth at which the experiments were conducted.
Table 1: Nodule Mining Experiments
|MESEDA (Deep Metaliferous Sediment Development Programme)
|DOMES (Deep Ocean Mining Environmental Study)
||OMI, OMA, NOAA, USA
||Eastern Pacific Ocean
|DISCOL / ATESEPP (Disturbance and reCOLonisation experiment)
||TUSCH Research Group, BMBF, Germany
||Deep South Pacific (Peru Basin)
|NOAA-BIE (National Oceanic and Atmospheric Administration - Benthic Impact Experiments)
||Clarion Clipperton Fracture Zone (CCFZ)
|JET (Japan deep-sea impact ExperimenT)
||Inter-Ocean Metal Consortium
|INDEX (Indian Deep-sea Environment Experiment)
||National Institute of Oceanography, India
||Central Indian Ocean Basin
|DIETS (Direct Impact ExperimenT on Seamount)
||Near Minami-Tori-Shima Island
Adapted from Sharma (2005)
* Includes Baseline Studies
POTENTIAL ENVIRONMENTAL IMPACTS OF DSM
The potential impacts from DSM have been divided into five overall categories: direct physical disturbance, sediment plumes, acoustic impacts, waste water disposal, and machinery leaks or malfunction. The table below shows categorical impacts and identified resources in DSM.
Table 2: Categorical Impacts and Identified Sources
(Source: Potential Deep-Sea Mining of Seafloor Massive Sulfides: A Case Study in Papua New Guinea)
POLITICAL AND LEGAL ASPECTS
One of the limiting factors associated with deep sea mining is the complex political and legal aspects involving exploration and marketing of sea bed minerals. More information on legal and political aspects can be found at the following links:
INVESTORS AND SUPPLIERS
Here is information about some of the main companies currently involved in deep sea mining.
Nautilus Minerals: The first company to commercially explore the seafloor for massive sulphide systems with the development of their Solwara 1 project in the Bismark Sea, Papua New Guinea. In January 2011, the company reported the presence of high grade mineralization with gold grades of up to 20.8 g/mt and copper grades of up to 37.7%. Nautilus Minerals was also granted an exploration license in the highly prospective Clarion Clipperton Fracture Zone (CCZ) of the Central Pacific. The company is also doing exploration work in waters near Tonga.
Neptune Minerals: Since 2011, they have been exploring and developing Seafloor Massive Sulfide (SMS) deposits. They claim that their operational approach and their extraction methods are two key aspects that differentiate them from other SMS exploration companies. Visit their website for more details on their work.
OceanfLORE: OceanflORE provides integrated contract mining solutions for offshore mine owner(s) to monetize their deposit through operational expenses rather than capital expenses.
IHC Merwede: IHC is focused on the continuous development of design and construction activities for the specialist maritime sector. It claims to be the global market leader for efficient dredging and mining vessels and equipment. They have developed deep sea mining systems that can reach depths of 5,000 m.
DEME: Based in Belgium, DEME (Dredging, Environmental and Marine Engineering) is an international group of specialized companies in the field of capital and maintenance dredging, land reclamation, port infrastructure development, offshore related services for the oil & gas industry, far shore windfarm installation and environmental remediation. DEME has also developed deepsea harvesting vessels.
LINKS AND PUBLICATIONS
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